In order to set up transportable provisional antennas and put them into service easily and rapidly, lightweight masts of a composite material, such as fibers associated with a resin, are increasingly being used to support these antennas.
When these masts are used they are kept upright by bracing means.
At the site where it is to be used, the mast is first laid on the ground, so it can be equipped with the antennas and the bracing cables.
Then in order to be raised, the mast is conventionally provided, first, with a collar articulated about a horizontal axis traversing this collar and a shoe anchored in the ground and, second, with at least one cable means fixed near the top of the mast, on which cable means traction is exerted from the base of the mast.
However, at the beginning of this operation, the rigging is substantially parallel to the mast and hence a very large tractional force must be exerted in order to obtain sufficient moment for raising the mast.
To overcome this disadvantage, it is known to associate a lever arm with the collar of the mast, perpendicular to the axis of the mast and in the plane in which the mast will be pulled upward; to the upper end of this arm are attached, first, one of the ends of the cable the other end of which is substantially fixed halfway up the mast and, second, the end of a cable the other end of which is grasped by a traction means such as a winch.
In order to be associated with the collar of the mast, this arm is generally provided at its lower end with a lower fork which laterally covers the mast or its collar and the cap support of its shoe anchored in the ground, so that it can benefit from being pivoted about the same axis as this mast collar when it accompanies the mast as it is pulled upward.
Under the combined effect of the tractional force and the weight of the antennas at the top of the mast, the mast undergoes a deformation which may become permanent, depending on its intensity, or even cause the mast to break.
Furthermore, in order to be effective, a lever arm of this kind must have a considerable length, on the order of several meters, which unfortunately makes the top of the arm quite high and makes it difficult to affix both the cable that is connected to the mast and the cable that is connected to the winch.